Everyone wants to talk about the finish line.
When people land on the island, the first questions are usually about the Koh Tao’s dive masters’ lifestyle or how much a divemaster course costs. It makes sense. The idea of trading an office chair for a tank and a regulator is the dream.
But there is a flaw in the "Zero to Hero" logic.
Most people focus entirely on the "Hero" part (the professional certification). They treat the "Zero" part (the Open Water course) as just a hurdle to clear as fast as possible.
That is a mistake.
If you are serious about a divemaster course, Koh Tao style, you need to look at the mechanics of your very first few days underwater. Specifically, you need to look at your depth limits.
The Standard 18m Ceiling vs. The 20m Standard
Here is a detail most beginners miss.
The global industry standard for an “Open Water Certification” is 18 meters. It’s fine for holiday divers who just want to see a turtle and go home.
But if you want to be a professional, those standards can feel limiting.
This is why some specific programs, like the RAID system used by schools like La Bombona, certify you to 20 meters right from the start.
Why do those extra two meters matter?
It isn't just about going deeper. It’s about the physics and physiology you learn to get there. Handling yourself at 20 meters requires a slightly sharper focus on air consumption and buoyancy than at 18 meters. It forces you to be a better diver before you even sign up for your first professional module.
Small Groups Build Better Pros
Another factor is the ratio.
In massive classes, you don't really swim. You just kneel on the bottom and wait for everyone else to finish. It kills the experience.
A future Divemaster cannot learn in a queue. You have to be off the bottom, controlling your own body weight, instead of just using the sand as a crutch.
So, look for courses that cap their groups. We are talking about a maximum of two or three students per instructor. This ensures that when you do your "Physics and Physiology" theory modules—and yes, you need to actually understand the physics, not just pass the quiz—you have someone there to explain how it applies to your body.
The Confidence Gap
Then there is also a huge difference in how you feel underwater. When you stick to the standard 18-meter limit, you often feel like a guest in the ocean. You tend to play it safe. But going down to 20 meters with a pro watching you changes your mindset.
You stop worrying about the deep water much faster. When you realize that you can handle the pressure—literally. You get used to checking your computer more often because you have to. You get used to the slightly darker water.
And here is the thing: A Divemaster cannot be a timid diver. You are the one people look at when they are scared. If you spent your entire Open Water course staying in the safe zone, you won't have that natural confidence to project to your students later. You build that "leader mindset" by challenging yourself in the deep end from day one, not day 60.
The Cost Question
So, how much is a divemaster course really?
Most places charge about 40,000 THB. However, if you pick the wrong one, you end up paying for it with your time. You don't want to spend your training just trying to unlearn mistakes.
If you rush your Open Water course in a big group with shallow limits, you will spend the first weeks of your divemaster training fixing your trim and air consumption.
If you start with a course that pushes you to 20 meters and keeps the groups small, you start your professional training ahead of the curve.
The Bottom Line
It is tempting to save money, but don't. You need to learn good habits immediately. That means finding a course with deeper limits and smaller groups.